Punch and die set

ABSTRACT

A punch and die set includes a die including two arms. The two arms and a bottom of the die define a die channel. A punch is sized to be received in the die channel. A rocker element is movably secured to the die. A reduced frictional element is movably secured to the rocker element. The rocker element is movably secured to the die so that the rocker element pivots relative to the die around a pivot point between a centerline of the die channel and at or inside a first of the arms.

This application claims the benefit of U.S. Provisional Application No. 61/545,223, filed Oct. 10, 2011, which is hereby incorporated by reference.

BACKGROUND

The present invention relates to a punch and die set. It finds particular application in conjunction with a punch and die set having a rocker element and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.

Bending is a manufacturing process that produces a shape along an axis in a ductile material such as metal. A punch and die set is commonly used for bending metal. A work piece (e.g., metal sheet) is positioned over a die set and a punch presses the work piece into the die set to form a shape. Residual stresses of the bending process may cause the work piece to spring back towards its original position. Therefore, it is not uncommon to over-bend the work piece to achieve a desired bend angle.

The present invention provides a new and improved apparatus and method which addresses the above-referenced problems.

SUMMARY

In one aspect of the present invention, a punch and die set is contemplated to include a die having two arms. The two arms and a bottom of the die define a die channel. A punch is sized to be received in the die channel. A rocker element is movably secured to the die. A reduced frictional element is movably secured to the rocker element. The rocker element is movably secured to the die so that the rocker element pivots relative to the die around a pivot point between a centerline of the die channel and at or inside a first of the arms.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings which are incorporated in and constitute a part of the specification, embodiments of the invention are illustrated, which, together with a general description of the invention given above, and the detailed description given below, serve to exemplify the embodiments of this invention.

FIG. 1 illustrates a schematic representation of a punch and die set in a first position in accordance with one embodiment of an apparatus illustrating principles of the present invention;

FIG. 2 illustrates a schematic representation of the punch and die set in a second position in accordance with one embodiment of an apparatus illustrating principles of the present invention; and

FIG. 3 is illustrates a work piece bent by the punch and die set.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENT

FIG. 1 illustrates a simplified component diagram of an exemplary punch and die set 10 in a rest position in accordance with one embodiment of the present invention. FIG. 2 illustrates the simplified component diagram of the exemplary punch and die set 10 in an actuated position in accordance with one embodiment of the present invention.

With reference to FIGS. 1 and 2, the punch and die set 10 includes an outer die 12 including two (2) arms 14, 16, respectively, and a bottom 20. The first arm 14 includes a first inner wall 22, and the second arm 16 includes a second inner wall 24. The arms 14, 16 and bottom 20 define an outer die channel 26. The outer die channel 26 defines a die entry 30 between the first and second inner walls 22, 24. A first rocker element 32 is movably secured to the first 14 arm (e.g., the inner wall 22 of the first arm 14). A second rocker element 34 is movably secured to the second 16 arm (e.g., the inner wall 24 of the second arm 16).

The arms 14, 16 and the rocker elements 32, 34, which are movably secured to the arms 14, 16, define a rocker channel 36, which is substantially symmetrical around a first axis 40 defined vertically along a centerline of the outer die channel 26. The outer die channel 26 houses the rocker elements 32, 34 and is sized to accommodate a desired punch radius, plus the rocker elements 32, 34, and an allowance for the desired thickness range of a work piece 42 to be bent in the die 12. Additional clearance may be added to facilitate ease of removal of the finished part upon completion of the bend and the subsequent springback of the work piece 42.

In the illustrated embodiment, a first spring mechanism 44 is used to movably attach the first rocker element 32 to the first arm 14. A second spring mechanism 46 is used to movably attach the second rocker element 34 to the first arm 16.

A punch 50 is sized to be received in the channel 26. The punch 50 is illustrated in a retracted position in FIG. 1. The punch 50 is illustrated in an extended position in FIG. 2. The punch 50 is moved between the retracted (FIG. 1) and extended (FIG. 2) positions via a stem 52. It is to be understood the stem 52 is mechanically moved between the retracted position (FIG. 1) and the extended position (FIG. 2) via a machine (e.g., a hydraulic machine) (not illustrated).

Although the punch 50 is illustrated as round, it is to be understood other shapes for the punch 50 are contemplated to accommodate fabrications of different degrees of complexity. For example, the punch may be shaped for partial closure forms, C-forms, return bends, etc.

With further reference to FIGS. 1 and 2, a first reduced frictional element 54 is movably secured to the first rocker element 32. A second reduced frictional element 56 is movably secured to the second rocker element 34. In one embodiment, the first and second reduced frictional elements 54, 56 are rollers or bearings (e.g., roller bearings) that are secured to the first and second rocker elements 32, 34, respectively. For example, the first and second reduced frictional elements 54, 56 are movably secured to the first and second rocker elements 32, 34 by first and second pins 60, 62, respectively. The first pin 60 defines a first axis 64 of the first reduced frictional element 54. The second pin 62 defines a second axis 66 of the second reduced frictional element 56.

The outer die 12 includes first and second pivot protrusions 70, 72 (ledges), respectively. The first pivot protrusion 70 is in the channel 26 between the first axis 40 defined vertically along the centerline of the channel 26 and a second axis 74, which is parallel to the first axis 40, defined at or inside the first inner wall 22 of the first arm 14. The second pivot protrusion 70 is in the channel 26 between the first axis 40 and a third axis 76, which is parallel to the first axis 40, defined at or inside the second inner wall 24 of the second arm 16. Because the second axis 74 is at or inside the first inner wall 22 and because the third axis 76 is at or inside the second inner wall 24, the second and third axes 74, 76 and the first and second pivot protrusions 70, 72 are inside the entry 30 of the die 12.

Optionally, the first pivot protrusion 70 is positioned so that the second axis 74 is at the first axis 64 of the first reduced frictional element 54, or between the first axis 64 of the first reduced frictional element 54 and the first axis 40 (e.g., the centerline of the channel 26). In this case, the second pivot protrusion 70 is positioned so that the third axis 74 is at the second axis 66 of the second reduced frictional element 56, or between the second axis 66 of the second reduced frictional element 56 and the first axis 40 (e.g., the centerline of the channel 26).

It is contemplated that the first and second pivot protrusions 70, 72 are substantially equally spaced from the first axis 40 along a surface of the channel 26. As discussed in more detail below, the substantially equal spacing of the first and second pivot protrusions 70, 72 from the first axis 40 results in the work piece 42 being bent in a substantially symmetrical manner.

The first rocker element 32 includes a first pivot recess 80 that cooperatively mates with the first pivot protrusion 70 of the outer die 12. A first pivot point 82 is based on (defined at) the first pivot protrusion 70. When the first pivot recess 80 of the first rocker element 32 cooperatively mates with the first pivot protrusion 70 of the outer the 12, the first rocker element 32 pivots relative to the outer die 12 at the first pivot point 82 (e.g., around the first pivot point 82).

The second rocker element 34 includes a second pivot recess 84 that cooperatively mates with the second pivot protrusion 72 of the outer die 12. A second pivot point 86 is based on (defined at) the second pivot protrusion 72. When the second pivot recess 84 of the second rocker element 34 cooperatively mates with the second pivot protrusion 72 of the outer die 12, the second rocker element 34 pivots relative to the outer die 12 at the second pivot point 86 (e.g., around the second pivot point 86).

During use, the work piece 42 (e.g., a metal sheet) to be bent is positioned across a top of the die 12 so that the work piece 42 passes over the die entry 30. As illustrated in FIG. 1, the punch 50 is positioned over the work piece 42. In this example, it is desirable to make a first bend 90 and a second bend 92 in the work piece 42, which are shown in FIG. 2. It is contemplated that the first and second bends 90, 92, respectively, together cooperate so that the work piece 42 is bent about 180° into a U-shape channel.

To achieve the first and second bends 90, 92 in the work piece 42, the punch 50 is moved downward from the position illustrated in FIG. 1 toward the position illustrated in FIG. 2. As the punch 50 is moved downward, the punch 50 contacts the work piece 42. As the work piece 42 is pushed into the rocker channel 36 in the die 12, the work piece 42 contacts the first and second reduced frictional elements 54, 56 and begins to bend. The first and second reduced frictional elements 54, 56 reduce friction against the work piece 42 as the work piece 42 bends while being pushed into the rocker channel 36. In addition, the first and second pivot protrusions 70, 72 are positioned as discussed above to reduce a tendency of the first and second rocker elements 32, 34 to collapse inward as the punch 50 begins to push the work piece 42 downward into the rocker channel 36. Reducing this tendency of the first and second rocker elements 32, 34 to collapse inward reduces any spikes in press tonnage or absolute interference as the punch 50 and work piece 42 enter the rocker channel 36. The symmetry of the rocker elements 32, 34 around the centerline first axis 40 also helps to equally transfer bending loads to the pivot points 82, 86.

In the illustrated embodiment, the first and second pivot protrusions 70, 72 are substantially squared-off ledges, which reduce and/or eliminate undesirable spreading movement of the rocker elements 32, 34 as the work piece 42 is pushed into the rocker channel 36. The positions of the first and second pivot protrusions 70, 72 also helps reduce and/or eliminate the undesirable spreading movement of the rocker elements 32, 34 as the work piece 42 is pushed into the rocker channel 36.

As the punch 50 moves farther downward into the rocker channel 36, the work piece 42 continues engaging the first and second reduced frictional elements 54, 56 and continues bending. At the same time, the first and second rocker elements 32, 34 begin pivoting around the first pivot point 82 and the second pivot point 86, respectively. The first and second reduced frictional elements 54, 56 reduce sliding friction in which the work piece 42 must slide under pressure in the rocker channel 36. Therefore, the first and second reduced frictional elements 54, 56 reduce the force required to push the work piece 42 into the rocker channel 36 and reduce and/or eliminate galling and other friction related cosmetic issues. The first and second reduced frictional elements 54, 56 are sized to calculated loads that will be experienced in the bending process. The gauge of the work piece 42 is based on the size of the die entry 30 and the radius formed. Therefore, multiple gauge thicknesses of a work piece 42 may be used in the same die 12.

As illustrated in FIG. 2, the pivoting action of the first and second rocker elements 32, 34 causes the work piece 42 to bend more than 90° at the first bend 90 and also bend more than 90° at the second bend 92 when the punch 50 is fully inserted into the rocker channel 36 to create the 180° U-shaped bend. Since the top portions of the first and second rockers 32, 34 (e.g., the ends of the first and second rockers 32, 34 including the first and second reduced frictional elements 54, 56) pivot inward toward the centerline of the channel 26, the stem 52 of the punch 50 is sized to be narrow enough to fit between the first and second reduced frictional elements 54, 56 when the first and second rockers 32, 34 pivot inward.

Since the desired bend at both the first bend 90 and also at the second bend 92 is about 90°, the over-bending (bending more than 90° at the first bend 90 and also bending more than 90° at the second bend 92) is desired to compensate for the work piece 42 tending to return (springback) to the original shape (e.g., before the work piece 42 was bent) after the punch 50 is removed from the rocker channel 36 and after the work piece 42 is removed from the punch 50. As illustrated in FIG. 3, the springback results in the work piece 42 having the desired bend of about 180° forming a U-shaped channel. The dotted lines 42 a in FIG. 3 illustrate the over-bend in the work piece 42 before the springback.

It is contemplated that once the punch 50 continues traveling downward until hitting respective bottom surfaces 94, 96 of the rocker elements 32, 34. Alternatively, it is contemplated that the distance the punch 50 travels into the rocker channel 36 may be used to control the degree of resulting over-bend. Because of the natural range of movement that may be designed into the rocker element, and the degree of bend being controlled by how deep the punch 50 enters the rocker channel 36, less tight clearances are required than in the prior art between the punch 50 and any sidewall elements of either the rocker channel 36 or the rocker elements 32, 34.

While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept. 

I/We claim:
 1. A punch and die set, comprising: a die including two arms, the two arms and a bottom of the die defining a die channel; a punch sized to be received in the die channel; a rocker element movably secured to the die; and a reduced frictional element movably secured to the rocker element, the rocker element being movably secured to the die so that the rocker element pivots relative to the die around a pivot, point between a centerline of the die and at or inside a first of the arms.
 2. The punch and die set as set forth in claim 1, wherein: the reduced frictional element is a roller that reduces friction against a work piece as the work piece is pushed into the die channel by the punch.
 3. The punch and die set as set forth in claim 2, wherein: the pivot point is between the centerline of the die channel and a rotational axis of the reduced frictional element.
 4. The punch and die set as set forth in claim 2, wherein: the reduced frictional element is a bearing that reduces friction against the work piece as the work piece is pushed into the die channel by the punch.
 5. The punch and die set as set forth in claim 1, wherein: the die includes a pivot protrusion; the rocker element includes a pivot recess that cooperates with the die pivot protrusion; and the pivot point is based on the pivot protrusion.
 6. The punch and die set as set forth in claim 1, further including: a second rocker element secured to the die; wherein the rocker element is secured to the first arm of the die; and wherein the second rocker element is secured to a second of the arms of the die.
 7. The punch and die set as set forth in claim 6, wherein: the rocker element and the second rocker element define a rocker channel as substantially symmetrical.
 8. The punch and die set as set forth in claim 7, further including: a second reduced frictional element movably secured to the second rocker element, the second rocker element being movably secured to the die so that the second rocker element pivots relative to the die around a second pivot point between the centerline of the die channel and at or inside the second arm.
 9. The punch and die set as set forth in claim 8, wherein: the reduced frictional element and the second reduced frictional element reduce friction against a work piece as the work piece is pushed into the rocker channel by the punch; the rocker element pivots around the pivot point and the second rocker element pivots around the second pivot point as the work piece is pushed into the rocker channel by the punch; and the pivoting of the rocker element and the second rocker element cause the work piece to over-bend to more than a 180° U-shaped channel while the work piece and the punch are in the rocker channel, so that the work piece is bent to about a 180° U-shaped channel after the punch is removed from the rocker channel and the work piece.
 10. The punch and die set as set forth in claim 1, further including: a spring mechanism movably securing the rocker element to the first arm of the die.
 11. A method of bending a work piece in a punch and die set, the method comprising: positioning a work piece above a rocker channel of a die and between the die and a punch; moving the punch to push the work piece into the rocker channel; as the work piece is entering the rocker channel, passing the work piece against a reduced frictional element; as the work piece is entering the rocker channel, pivoting a rocker element relative to the die around a pivot point between a centerline of the rocker channel and at or inside a first arm of the die.
 12. The method of bending a work piece in a punch and die set as set forth in claim 11, further including: over-bending the work piece beyond about a 180° U-shaped channel while the work piece and the punch are in the rocker channel, so that the work. piece is bent to about a 180° U-shaped channel after the punch is removed from the rocker channel and the work piece.
 13. The method of bending a work piece in a punch and die set as set forth in claim 12, further including: removing the punch from the rocker channel; and removing the work piece from the punch and allowing the work piece to return to about a 180° U-shaped channel bend.
 14. The method of bending a work piece in a punch and die set as set forth in claim 11, further including: as the work piece is entering the rocker channel, pivoting a second rocker element relative to the die around a second pivot point between a centerline of the rocker channel and at or inside a second arm of the die.
 15. The method of bending a work piece in a punch and die set as set forth in claim 11, wherein the step of passing the work piece against a reduced frictional element includes: rolling a bearing against the work piece.
 16. A punch and die set, comprising.: a die including two arms, the two arms and a bottom of the die defining a rocker channel; a punch sized to be received in the rocker channel; a first rocker element movably secured to a first of the arms; a first reduced frictional element movably secured to the first rocker element, the first rocker element being movably secured to the first arm so that the rocker element pivots relative to the die around a first pivot point between a centerline of the rocker channel and at or inside the first arm; a second rocker element movably secured to a second of the arms; and a second reduced frictional element movably secured to the second rocker element, the second rocker element being movably secured to the second arm so that the second rocker element pivots relative to the die around a second pivot point between the centerline of the rocker channel and at or inside the second arm.
 17. The punch and die set as set forth in claim 16, wherein: the respective positions of the first and second pivot points between the centerline and at or inside of the respective arms results in relatively less force required by the punch to push a work piece into the rocker channel.
 18. The punch and die set as set forth in claim 16, wherein: the first rocker element and the second rocker element define the rocker channel as substantially symmetrical.
 19. The punch and die set as set forth in claim 16, wherein: the pivoting of the first rocker element causes a first over-bend in the work piece while, the work piece and the punch are in the rocker channel; the pivoting of the second rocker element causes a second over-bend in the work piece while the work piece and the punch are in the rocker channel; the first and second over-bends create more than about a 180° over-bend U-shaped channel; and the first and second over-bends return to first and second bends after the work piece is removed from the rocker channel and the punch to create about a 180° bend U-shaped channel.
 20. The punch and die set as set forth in claim 19 wherein: the first and second bends are substantially symmetrical. 